基于自下而上法制备的氮掺杂石墨烯量子点及其光催化性能研究

发布时间：2018-04-09 10:34

本文选题：氮掺杂石墨烯量子点　切入点：上转换发光性能　出处：《江苏大学》2017年硕士论文

【摘要】：石墨烯量子点作为一种新型的发光碳纳米材料,是目前研究的重点和热点之一。与传统的半导体量子点相比,石墨烯量子点既有其良好的荧光性能,又具有碳材料天然的无毒性。此外,其表面因含官能团而易于溶剂分散和改性应用。基于石墨烯量子点优异的性能,其在各个领域尤其是光催化方面体现出了重要的价值。石墨烯量子点合成方便,无毒性及稳定的荧光特性尤其是上转换发光特性,并且还能改善催化剂的光催化活性。因此,石墨烯量子点在光催化领域的实际应用有着十分明显的优势。基于以上分析,我们制备了氮掺杂石墨烯量子点(NGQDs),以及开展了氮掺杂石墨烯量子点/钒酸铋复合物、氮掺杂石墨烯量子点/纳米Ag/钒酸铋三元复合物的制备工艺及光催化性能方面的研究和探索。具体工作如下:(1)以一水合柠檬酸和尿素分别作为碳源和氮源,在水热环境下通过热解法成功制备了荧光量子产率达到18.9%的氮掺杂石墨烯量子点(NGQDs)。该方法简单方便,且条件可控,制备出来的NGQDs发蓝色荧光。我们通过延长反应时间来调控NGQDs的尺寸,从而实现对其光学性质的调控研究。然后,借助于一系列的形貌、结构和光学表征手段,系统分析了NGQDs的尺寸与荧光性能之间的联系。并且我们探究pH值的大小对NGQDs荧光强度的影响,得知在中性条件下NGQDs的荧光最强。也研究了不同离子浓度和不同溶剂对NGQDs荧光强度的影响,实验结果表明不同离子浓度对其荧光强度无甚大影响,而不同溶剂则表现出了一定程度的荧光淬灭现象。并通过Zet a电位测定NGQDs具有良好的物理稳定性。(2)通过直接和简单的“自下而上”的方法,在水热条件下合成了具有优异发光性能的NGQDs。所制备的NGQDs表现出不依赖激发的上转换荧光特征。然后,又通过水热反应及沉积技术制备了NGQDs/BiVO_4复合光催化剂,并通过一系列表征手段证明NGQDs成功地负载在BiVO_4表面。通过光催化降解亚甲基蓝(MB)实验可得,复合光催化剂表现出增强的可见光光催化活性。NGQDs/BiVO_4复合物的光催化增强性能可以归因于NGQDs的上转换发光性能以及降低电子-空穴对的复合率。此外,该NGQDs/Bi VO4复合光催化剂显示出良好的稳定性。通过固体紫外、荧光及电化学检测等表征分析和自由基捕获实验研究了复合光催化剂的催化机理,揭示了材料界面的电子转移情况以及超氧自由基作为主要活性物质进行了光催化降解MB。(3)采用水热还原法和沉积法制备了NGQDs/Ag/BiVO_4三元复合纳米材料,基于纳米Ag的LSPR效应,构建了NGQDs/Ag/Bi VO4三元等离子体型复合物降解盐酸四环素(TC·HCl)的催化体系。由于纳米Ag的LSPR效应,光生电子和空穴得到了有效分离,其中,纳米Ag的电子存储作用、LSPR效应引起的直接电子迁移作用(DET)和能量迁移(PIR ET)三者的共同作用促使了电子-空穴对的分离。通过XRD、XPS、SEM和TEM对三元复合物进行了结构和形貌表征,利用电化学检测对所制备样品的电化学稳定性和载流子迁移情况进行了研究。同时自由基捕获实验和顺磁共振技术测试(ESR)检测证实了·O2-和·OH自由基是在光催化降解体系中的最主要的活性物质。也利用质谱对TC·HCl的反应中间产物进行了研究。基于以上的分析,我们对NGQDs/Ag/BiVO_4三元复合物在光催化降解TC·HCl过程中可能的电荷转移机理进行了系统分析和深入研究。
[Abstract]:A new type of luminescent carbon nano materials as graphene quantum dots, is one of the key and hot research. Compared with traditional semiconductor quantum dots, graphene quantum dots have good fluorescence properties, and is non-toxic natural carbon materials. In addition, the surface for easily dispersed and solvent containing functional groups the application of modification of properties. Graphene quantum dot based on its excellent, especially in the fields of photocatalytic show the important value. Graphene quantum dots synthesized convenient, non-toxic and stable fluorescence characteristics especially the luminescence properties of upconversion, and can improve the photocatalytic activity of the catalyst. Therefore, the actual application of graphite graphene quantum dots in the field of photocatalysis has very obvious advantages. Based on the above analysis, we prepared nitrogen doped graphene quantum dots (NGQDs) were prepared, and the nitrogen doped graphene quantum dots / vanadate Bi compound, to study and explore the preparation and photocatalytic performance of nitrogen doped graphene quantum dots / nano Ag/ three element bismuth vanadate complexes. The specific work is as follows: (1) with citric acid monohydrate and urea were used as carbon source and nitrogen source, the nitrogen doped graphene quantum dots pyrolysis was successfully prepared fluorescence quantum yield reached 18.9% in the hydrothermal environment (NGQDs). This method is simple and convenient, and controllable conditions, the synthesized NGQDs blue fluorescence. We by prolonging the reaction time to control the size of the NGQDs, so as to realize the control of the optical properties. Then, with the help of morphology a series of methods, structural and optical characterization, system analysis between the size and fluorescence properties of NGQDs contact. And we explore the impact of pH value on the fluorescence intensity of NGQDs, that NGQDs had the strongest fluorescence under neutral conditions. Also studied Influence of concentration and different solvents on the fluorescence intensity of NGQDs, the experimental results show that the different ion concentration without great influence on its fluorescence intensity, and different solvents showed fluorescence quenching degree of arc phenomenon. And through the Zet a potential determination of NGQDs with physical stability is good. (2) through a direct and simple method the "bottom-up", was synthesized under hydrothermal conditions with excellent luminescent properties of NGQDs. prepared by NGQDs showed no dependence on the excitation of the luminescence characteristics. Then, through the NGQDs/ BiVO_4 composite photocatalyst prepared by hydrothermal reaction and deposition process, and through a series of characterization means that NGQDs successfully the load on the surface of BiVO_4. The photocatalytic degradation of methylene blue (MB) experiment, the composite photocatalyst exhibited photocatalytic photocatalytic activity of.NGQDs/BiVO_4 composite material enhanced performance can be enhanced To attribute to NGQDs upconversion luminescence properties and reduce the recombination rate of electron hole pairs. In addition, the NGQDs/Bi VO4 composite photocatalyst exhibited good stability. By UV, fluorescence and electrochemical detection and characterization analysis of free radical trapping experiment on the catalytic mechanism of composite photocatalyst was revealed and superoxide free radical electron transfer material interface as the main active substance of the photocatalytic degradation of MB. (3) NGQDs/Ag/BiVO_4 three composite nano materials were prepared by reduction method and hydrothermal deposition method, the LSPR effect of nano Ag on the construction of degradation of complex NGQDs/Ag/Bi VO4 three plasma type (TC - HCl) tetracycline catalysis system. Due to the LSPR effect of Ag nanoparticles, the photogenerated electrons and holes were effectively separated from the electronic storage effect of nano Ag, direct electron transfer effect caused by LSPR The role of (DET) and energy transfer (PIR ET) three together promote the separation of electron hole pairs. By XRD, XPS, the structure and morphology of the composites were three yuan SEM and TEM on the electrochemical stability and mobility of sample preparation were studied by electrochemical detection. At the same time, free radical trapping experiment and magnetic resonance imaging (ESR) detection test confirmed that O2- and OH free radical is the main active substance in the photocatalysis system. Also the use of mass spectrometry in TC HCl reaction was investigated. Based on the above analysis, we have to charge three yuan compound NGQDs/Ag/BiVO_4 in the photocatalytic degradation of TC and HCl in the process of transfer mechanism was analyzed and studied.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TB383.1

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